#include <iostream>
#include <stack>
#include <cstdio>
#include <vector>
#include <algorithm>

#define x first
#define pdd pair < double, double >
#define y second

using namespace std;

const int NMax = 120005;
pair < double, double > v[NMax];
vector < pair < double, double > > st;
int N;

void Read()
{
    scanf("%d",&N);
    for(int i=1; i<=N; ++i)
    {
        scanf("%lf%lf", &v[i].x, &v[i].y);
    }
}

void Select_Mini()
{
    for(int i=2; i<=N; ++i)
        if(v[1] < v[i])
            swap(v[1],v[i]);
}

double Det(pair < double, double > a,
           pair < double, double > b,
           pair < double, double > c)
{
    return (b.y-a.y)*(c.x-b.x)-(c.y - b.y)*(b.x-a.x);
}

bool cmp(pair < double, double > x, pair < double, double > y)
{
    return Det(v[1],x,y) < 0;
}

int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);


    Read();
    Select_Mini();
    sort(v+2, v+N+1, cmp);

    int sz;
    for(int i=1; i<=N; ++i)
    {
        sz = st.size();
        while(st.size() >=2 && Det(st[sz-2],st[sz-1],v[i]) > 0)
        {
            st.pop_back();
            sz = st.size();
        }

        st.push_back(v[i]);
    }

    printf("%d\n",st.size());

    for(int i=0; i<st.size(); ++i)
    {
        printf("%lf %lf\n",st[i].first,st[i].second);
    }


    return 0;
}